(1) Field of the Invention
The present invention relates to the techniques, in an image reader of the flat bed scanning type using a CCD (charge coupled device) line sensor, of displaying optical indicators on a table to which an original is set. More particularly, the invention relates to the techniques applicable to;
(a) displaying an effective image reading area corresponding to a copying magnification ratio when enlargement selection is made for a reproduction image by varying projecting magnification of an input optical system with respect to the CCD line sensor,
(b) setting an original to a document table at a desired with a main scanning direction, and
(c) designating trimming areas within an original.
(2) Description of the Prior Art
(a) FIG. 16 is a schematic view of an input scanning system incorporated into a conventional apparatus. FIG. 17 is a view showing an effective image reading area displayed on the conventional apparatus.
As shown in FIG. 16, the image reader of the flat bed scanning type includes a document table 1 movable in a sub-scanning direction (leftward in FIG. 16) and having a glass plate 2 to which an original to be read is set. Light flux (transmitted or reflected) from the original is passed through a linear slit for shaping, and through an input optical system including, for example, reflecting mirrors 3, 4 and 5 and a zoom lens 6, for image formation to a CCD line sensor 7. The CCD line sensor 7 includes a multiplicity of sensor elements arranged in a main scanning direction (perpendicular to the plane of the drawing), and reads the image by self-scanning these elements in the main scanning direction.
In such an image reader, enlargement selection is made by varying magnification of the zoom lens 6 to vary image areas of the original projected for image formation to the CCD line sensor 7.
When the optical magnification of the zoom lens 6 is set to double, for example, an image area is projected in half size to the CCD line sensor 7. As a result, the original size is doubled.
Similarly, when the optical magnification of the zoom lens 6 is set to half, the image area is projected in double size to the CCD line sensor 7, which results in a halved original size.
In order to read the original without deteriorating quality of the input image, the zoom lens 6 is driven to project the image over an entire effective pixel region of the CCD line sensor 7 regardless of the selected optical magnification.
When the zoom lens 6 is driven to vary magnifications as above, naturally the angle from which the zoom lens 6 views the original changes. This will readily be understood by the analogy that a zooming operation through a zoom lens attached to a single reflex camera changes the range of view seen through a viewfinder.
For the reason noted above, in the image reader of the flat bed scanning type, the effective image reading area varies in the main scanning direction with driving of the zoom lens 6 for a variation in magnification. It is therefore necessary, when setting an original to the glass plate 2 of the document table 1, to take the reproducing magnification (i.e. the magnification of the input optical system) into account and place the original within the effective image reading area.
As shown in FIG. 17, the document table 1 has a marker 8 provided on one side thereof to indicate an effective image reading area corresponding to a reproducing magnification. An original is set within the area (hatched in FIG. 17) defined between phantom lines 9a and 9b extending in the sub-scanning direction from opposite ends of the marker 8.
Further, in the copying camera disclosed in Japanese Patent Publication No. 15050/1989, a copying material supporting member defines bores in appropriate peripheral positions thereof, and an optical fiber is connected to these bores to form light emission points. A plurality of spotlights emitted from the light emission points are projected to a document table through an optical system to indicate a position for setting an original.
With the known apparatus shown in FIGS. 16 and 17, however, it is necessary to draw a plurality of markers corresponding to individual reproducing magnifications or to draw one marker having a plurality of graduations for showing effective image reading areas for the respective magnifications. In either case, the operator has difficulties in visually recognizing a correct marker or graduation corresponding to a selected reproducing magnification.
According to this apparatus, since the marker 8 is drawn outwardly of the glass plate 2 to which an original is set, the operator must use his or her own judgment to determine the phantom lines 9a and 9b shown in FIG. 17 for placing the original therebetween. This presents the problem of low original setting precision.
In the apparatus disclosed in Patent Publication No. 15050/1989, the spotlights are projected through the input optical system back to the document table for indicating the original setting positions, with spotlight images variable in accordance with reproducing magnifications. This apparatus may be said an improvement upon the illustrated known apparatus with regard to the cumbersome original setting operation. However, the operator must determine lines linking these spotlight images for setting an original within the area thus defined. An original can hardly be set promptly and precisely in this way.
The spot-like light emission points for indicating original setting positions are available only for an apparatus such as a copying camera which has a relatively large photosensitive area. In an apparatus such as an image reader of the flat bed scanning type which employs a small image pickup device such as a CCD line sensor for providing a photosensitive area, it is practically difficult to include spot-like light emission points in the effective pixel region of the CCD line sensor.
(b) In the known image reader of the flat bed scanning type, the following two methods are used to produce a layout with a read image inclined at an angle with the main scanning direction:
One such method consists in rotation of the original (image) effected through image processing as practiced with page-makeup scanners. Specifically, read image information is stored in a memory medium such as a magnetic disk, and the image is rotated by image processing on the memory. Such image processing, however, requires the memory medium to have a very large capacity for storing image information, which results in high cost of the apparatus.
In the other method, as disclosed in Japanese Patent Laying-Open Publication No. 49046/1989, the document table supporting an original is itself rotated. However, the method of rotating the document table requires a mechanism for supporting the document table to be rotatable with high precision and a mechanism for detecting rotating angles. This poses the problem of complicating mechanical components of the apparatus and thus rendering the apparatus expensive.
(c) In the known image reader of the flat bed scanning type, trimming areas of an original are designated as follows:
This type of image reader includes a document table cover for pressing from above an original placed on the document table, and a trimming frame disposed on the table cover for designating trimming areas. The trimming frame comprises a transparent sheet defining lattice sections and attached to the table cover to be movable between open and closed positions.
For designating trimming areas of an original, the trimming frame is opened, the original is set face up in a selected position on the table cover, and then the trimming frame is closed. In this state, the original and the lattice sections superposed thereon are visually observable from above the transparent trimming frame.
The operator, utilizing the lattice sections, reads coordinates of desired trimming areas of the original, and designates the trimming areas by inputting the coordinates through keys on a control panel.
According to the known apparatus, however, reading errors due to parallax tend to occur since the trimming areas of an original are visually read using the lattice sections. Thus, there is a problem of failing to assure precise designation of trimming areas.
In addition, designation of trimming areas is a cumbersome and time-consuming task with the need to read coordinates of trimming areas and then key-input the coordinates.